Polyester polyols and polyether polyols nowadays have many uses as raw materials, including for production of paint resins which are utilized, for example, for the preliminary coating of metals. For this purpose, the polyols are generally dissolved in solvents and, after application to the metal, crosslinked with melamine while heating, in the course of which the crosslinked polyester adheres to the metal and the solvent evaporates.
An essential factor for the adhesion is the nature of the substrate, i.e. generally the nature of the metal. In many cases, the metals are soiled owing to processing steps, for example by oil residues. Residues of this kind lead to a distinct reduction in adhesion and wetting of the paint system on the metal. For this reason, in the current standard processes, intensive cleaning of the metals is required before the actual coating with the paint system. This additional cleaning is generally very inconvenient and laborious.
The problem addressed was thus that of providing systems which get around the disadvantages of the prior art mentioned.
Said problem is solved through the use of block copolymers according to the present invention. The present invention accordingly firstly provides for the use of block copolymers formed from OH-, COOH- or amino-functionalized polymers and polyesters as binders in coating compositions, preferably paints, especially for improvement of the adhesion of coatings, especially coil coatings on metals.
The present invention accordingly firstly provides for the use of block copolymers formed from OH-, COOH- or amino-functionalized polymers and polyesters as binders in coating compositions, wherein the OH-, COOH- or amino-functionalized polymers are selected from NH2- or NHR- or NR2-functionalized polyamides, NH2- or NHR- or NR2-functionalized polyamines, OH- or COOH-functionalized polystyrene or OH- or COOH-functionalized polyolefins, where R is identical or different organic radicals, preferably aliphatic or aromatic radicals having preferably 1 to 20 and more preferably 1 to 6 carbon atoms.